Gasket type orifice and pressure type flow rate control apparatus for which the orifice is employed

ABSTRACT

An orifice changeable pressure type flow rate control apparatus comprises a valve body of a control valve for a pressure type flow rate control apparatus installed between an inlet side fitting block provided with a coupling part of a fluid supply pipe and an outlet side fitting block provided with a coupling part of a fluid takeout pipe; a fluid inlet side of the valve body and the inlet side fitting block, and a fluid outlet side of the valve body and the outlet side fitting block are detachably and hermitically connected respectively so a flow passage for gases through the control valve is formed; and, a gasket type orifice for a pressure type flow rate control apparatus is removably inserted between a gasket type orifice insertion hole provided on the outlet side of the valve body and a gasket type orifice insertion hole of the outlet side fitting block.

FIELD OF THE INVENTION

The present invention relates to improvements in a gasket type orifice and a pressure type flow rate control apparatus for which the orifice is employed. The present invention relates more concretely to a gasket type orifice having a high precision hole diameter for which a thin metal plate is used so that it can be manufactured at low cost, with high efficiency and also with stability; a pressure type flow rate control apparatus for which a gasket type orifice is employed; and an orifice-replaceable pressure type flow rate control apparatus wherewith an orifice can be replaced leak-free and promptly, a flow rate range of the pressure type flow rate control apparatus can be changed easily after its field installation, and the flow rate control can be maintained with high accuracy within ±1% FS.

TECHNICAL BACKGROUND OF THE INVENTION

Conventionally, to make an orifice it has been common that an orifice hole is made directly on an orifice plate by means of mechanical processing and the like, the orifice plate is interposed in the pipe passage at an appropriate position on the joint portion of the pipe passage or the connecting portion of a device and a pipe passage, and it is directly clamped and fixed hermetically.

However, with the afore-mentioned orifice of the directly clamped fixing type there is potential that deformation is caused on the orifice plate due to clamping and fixing of the plate, thus making it difficult that an orifice plate is made thin enough. For this reason, it becomes difficult that a high precision orifice having a prescribed hole diameter and shape without uneven flow rate characteristics is manufactured with stability and at low cost when a thin orifice plate is used.

To solve the afore-mentioned difficulties, an orifice wherewith an orifice plate is welded to appropriate holding hardware, and the orifice plate welded to holding hardware is inserted into a pipe passage to be fixed has been developed.

However, there have arisen such shortcomings as that an orifice hole diameter might be altered by influence of heat caused at the time of welding, thermal stress might cause cracks on the thin orifice plate, and further corrosion resistance of the orifice plate is lowered.

As seen above, an orifice, particularly a high precision orifice having certain constraint with a shape, a hole diameter and the like which is employed with a pressure type flow rate control apparatus and the like is not able to be manufactured at low cost, and at the same time it is found structurally difficult to insert and fix in a pipe passage, thus causing various problems in practical use.

On the other hand, a pressure type flow rate control apparatus with which an orifice is a dispensable constituent member has excellent characteristics in responsivity, control accuracy, manufacturing cost, maintainability and the like when compared with those of a thermal type mass flow rate control apparatus (MFC) represented by a mass flow controller, and is widely used in such a technical field as semiconductor manufacturing.

FIG. 7( a) and FIG. 7( b) show a basic block diagram of the afore-mentioned conventional pressure type flow rate control apparatus FCS. The major portion of the pressure type flow rate control apparatus FCS comprises a control valve 2, a pressure detector 6, an orifice 8, flow rate computation circuits 13,31, a flow rate setting circuit 14, a computation control circuit 16, a flow rate output circuit 12 and the like.

In FIG. 7( a) and FIG. 7( b), 3 designates an orifice upstream side pipe, 4 a valve actuator, 5 an orifice downstream side pipe, 7 a temperature detector, 9 a valve, 15 a flow rate conversion circuit, 10, 11,22,28 amplifiers, 17,18,29 A/D converters, 19 a temperature correction circuit, 20,30 computation circuits, 21 a comparison circuit, Qc a computation flow rate signal, Qf switching computation flow rate signal, Qe a flow rate setting signal, Qo a flow rate output signal, Qy a flow rate control signal, Po gas supply pressure, P₁ orifice upstream side gas pressure, P₂ orifice downstream side gas pressure, and k a flow rate conversion rate.

The afore-mentioned pressure type flow rate control apparatus FCS in FIG. 7( a) is mainly used when the ratio P₁/P₂ of the orifice upstream side gas pressure P₁ and the orifice downstream side gas pressure P₂ is equal to the critical value of the fluid or lower than that (that is, when the gas flow is under critical conditions). The gas flow rate Qc going through an orifice 8 is given by Qc=KP₁ (where K is a proportional constant).

The afore-mentioned pressure type flow rate control apparatus FCS in FIG. 7( b) is mainly used for the flow rate control of the gas which becomes flow conditions both in critical and non-critical conditions. The gas flow rate Qc going through an orifice 8 is given by Qc= KP₂ (P₁−P₂) (where K is a proportional constant, and _(m) and _(n) are constants).

Furthermore, with the afore-mentioned pressure type flow rate control apparatus in FIG. 7( a) and FIG. 7( b), the flow rate setting value for the flow rate control is given by a voltage value with a flow rate setting signal Qe. For example, when the pressure control range 0˜3 (kgf/cm abs) of the upstream side pressure P₁ is presented by the voltage range 0˜5V, Qe=5V (a full scale value) becomes equivalent to the flow rate Qc=KP₁ in the pressure P₁ of 3 (kgf/cm abs).

Concretely, if a flow rate setting signal Qe=5V is inputted when the conversion rate k of the flow rate conversion circuit 15 is set at 1, a switching computation flow rate signal Qf (Qf=kQc) becomes 5V, and a control valve 2 is operated for opening and closing until the upstream side pressure P₁ reaches 3 (kgf/cm abs), thus resulting in that a gas of a flow rate Qc=KP₁ corresponding to P₁=3 (kgf/cm abs) flows through an orifice 8.

In the case that the range of pressure to control is switched to 0=2 (kgf/cm abs) and the pressure range is presented by the flow rate setting signal Qe of 0˜5V (that is, when a full scale value of 5V gives 2 (kgf/cm abs), the afore-mentioned flow rate conversion rate k is set at ⅔.

As a result, assuming that the flow rate setting signal Qe=5V is inputted, because of Qf=kQc, the switching computation flow rate signal Qf becomes Qf=5×⅔V, and a control valve 2 is operated for opening and closing until the upstream side pressure P₁ becomes 3×⅔=2 (kgf/cm abs).

Namely, a full scale flow rate is converted so that Qe=5V shows the flow rate Qc=KP₁ equivalent to P₁=2 (kgf/cm abs).

It is also same with the afore-mentioned pressure type flow rate control apparatus in FIG. 7( b). The flow rate Qc of the gas passing through an orifice 8 is given by Qc=KP₂ (P₁−P₂) (where K is a proportional constant, and _(m) and _(n) are constants). The afore-mentioned proportional constant K changes when the type of gases varies.

As stated above, with the conventional pressure type flow rate control apparatus, it is so constituted that a flow rate Qc=KP₁ under the orifice upstream side pressure P₁ corresponding to Qe=5V (full scale·F.S.) can be switched by adjusting the conversion rate k of the flow rate conversion circuits 15. However, the flow rate switching range is strictly within the range of the flow rate smaller than the flow rate Qc=KP₁ under the upstream side pressure P₁ corresponding to the afore-mentioned Qe=5V (F.S. value), and the flow rate Qc under the upstream side pressure P₁ becomes the flow rate value unequivocally determined by a constant k obtained with an orifice diameter and the like.

In other words, in order that the pressure control range 0˜3 (kgf/cm abs) under the orifice upstream side pressure P₁ is presented with the voltage range 0˜5V, and the flow rate value Qc at Qe=5V is switched up to the flow rate, for example, 5 times, it becomes necessary that an orifice itself needs to be changed to an orifice with a constant K having a value 5 times.

FIG. 8 shows an example of the afore-mentioned pressure type flow rate control apparatus, which makes it possible that an orifice can be replaced, wherewith an orifice insertion hole 24 is provided on the fluid outlet side of a valve body 23 of the control valve 2 which forms a pressure type flow rate control apparatus FCS, and an orifice 8 having an appropriate diameter is inserted replace-free into said orifice insertion hole 24, and hermeticity of the fluid passage 34 is secured through the mediation of pressing metal ware 32, a bearing 33 and a sealing material 35 a.

Patent Document 1: TOKU-KAI-HEI No. 8-338546

Patent Document 2: TOKU-KAI No. 2000-66732

Patent Document 3: TOKU-KAI No. 2000-322130

Patent Document 4: TOKU-KAI No. 2003-195948

Patent Document 5: TOKU-KAI No. 2004-199109

Now, with the afore-mentioned conventional pressure type flow rate control apparatus in FIG. 7( a) and FIG. 7( b), due to the reason that supply pressure Po for the fluid to be controlled is ordinary maintained at a set value, the maximum value Qc of the flow rate to be control is unequivocally determined by the orifice 8 to be used. So, unless the orifice itself is replaced, it is difficult that the maximum or minimum flow rate Qc of the afore-mentioned fluid is changed in a large scale.

Also, with FIG. 8, it is required that pressing metal ware 32 is removed each time when an orifice 8 is replaced, and in some cases sealing material 35 a is changed. To dismantle a piping passage is time consuming and difficult.

Furthermore, with the orifice replacement method in FIG. 8, it becomes very difficult to prevent the outside leak completely from a so-called orifice sealing part because it is so constituted that a sealing mechanism of an orifice 8 comprises a sealing material 35 a attached to the surface side of the orifice 8 and a touching seat 35 b for sealing on the valve main body side attached to the reverse face side of the orifice 5, and sealing characteristics of both faces of the orifice 8 are secured by the screw-in pressing pressure of the pressing metal ware 32.

In addition, another shortcoming is that an orifice plate cannot be very thin because it is so constituted, as stated before, that an orifice 8 is directly clamped and fixed even though, as shown in FIG. 8, a very thin metal made orifice plate is machine-processed to make an orifice with a prescribed inside diameter thereon, thus resulting in that it becomes difficult to manufacture a high-precision orifice at low cost.

Another difficulty is that, as stated before, distortion, cracks, corrosion and the like caused on the orifice plate with weld heat cannot be prevented though it is so constituted that orifice holding metal ware is welded to a thin orifice plate, and said orifice holding metal ware is caught to be fixed.

DISCLOSURE OF THE INVENTION Object of the Invention

It is a primary object of the present invention to solve the afore-mentioned shortcomings of a conventional orifice and a pressure type flow rate control apparatus for which the orifice is used, namely, that (a) it is difficult that an orifice having a prescribed diameter and a shape and also having stable flow rate characteristics is manufactured by using a thin orifice plate, (b) a deformation of an orifice and cracks on the orifice plate can be easily caused with a welding type orifice due to its thermal stress, (c) with a pressure type flow rate control apparatus for which an orifice is used, it is difficult to cope with substantial enlargement of a flow rate range only by changing a conversion rate k of the flow rate computation circuit, and (d) with a conventional orifice replacement type, it takes much time to replace an orifice, and there exists a high risk that an outside leak is caused, and the like, and to provide an orifice which makes it possible that highly accurate, stable flow rate characteristics are secured by using a very thin orifice plate, and it is held and fixed to the inside of a fluid passage easily and leak free, and it is manufactured at low cost and at ease, and also a pressure type flow rate control apparatus for which the orifice is used, and at the same time, to provide an orifice replaceable pressure type flow rate control apparatus which allows that even after the shipment from a factory, a flow rate range can be changed easily and promptly at worksite by replacing an orifice 8, the outside leak from the orifice 8 is completely eliminated, and the flow rate control accuracy is remarkably enhanced.

Means to Achieve the Object

A gasket type orifice as claimed in Claim 1 in the present invention is basically so constituted that an orifice base (38 a) equipped with a convex portion (38 a ₁) for fitting and an orifice base (38 b) equipped with a concave portion (38 b ₁) for fitting are combined, and an orifice plate (38 c) is hermetically inserted between the end faces of both orifice bases, and both end faces (38 a ₃), (38 b ₃) of both orifice bases (38 a), (38 b) are made to be sealing faces for the gasket.

A gasket type orifice as claimed in Claim 1 in the present invention is basically so constituted that a brim portion (38 d ₁) projected inwardly in the inside in the vicinity of one side of a short cylinder-shaped orifice base (38 d) for which end faces of both sides are made to be sealing faces, and a thin orifice plate (38 c) equipped with an orifice hole on the outside face of said brim portion (38 d ₁) is laser-welded and fixed over the entire periphery.

A pressure type flow rate control apparatus as claimed in Claim 3 in the present invention is basically so constituted that with a pressure type flow rate control apparatus (A) equipped with a control valve, a pressure detector, an orifice, a flow rate computation circuit and a computation control circuit, the afore-mentioned orifice is made to be a gasket type orifice as claimed in Claim 1 or Claim 2.

The invention as claimed in Claim 4 is so made that with a pressure type flow rate control apparatus as claimed in Claim 3, a valve body (23) of a control valve which forms a pressure type flow rate control apparatus (A) is hermetically connected with an inlet side block (40) having a fluid flow passage (40 a), a center block (41) equipped with a valve seat (2 b), and an outlet side block (42) equipped with an outlet side fluid passage (42 a).

The invention as claimed in Claim 5 is so made that with a pressure type flow rate control apparatus as claimed in Claim 4, an installation position of an orifice which constitutes a pressure type flow rate control apparatus (A) is made between the fluid outlet side of a center block (41) of a control valve and the fluid inlet side of an outlet side fitting block (42).

An orifice changeable pressure type flow rate control apparatus as claimed in Claim 6 is basically so constituted that a valve body 23 of a control valve 2 for a pressure type flow rate control apparatus A is installed between an inlet side fitting block 39 equipped with a coupling portion for a fluid supply pipe and an outlet side fitting block 43 equipped with a coupling portion for a fluid takeout pipe; said fluid inlet side of the valve body 23 and the afore-mentioned fluid outlet side of an inlet side fitting block 39, and also the afore-mentioned fluid outlet side of the valve body 23 and the afore-mentioned fluid inlet side of an outlet side fitting block 43 are hermetically connected with detachability respectively, thus forming a flow passage for gases through the afore-mentioned control valve 2, and a gasket type orifice 38 of a pressure type flow rate control apparatus A is inserted removably between a gasket type orifice insertion hole 42 c provided on the outlet side of the afore-mentioned valve body 23 and a gasket type orifice insertion hole 43 b provided on the fluid inlet side of the outlet side fitting block 43.

The invention as claimed in Claim 7 is so constituted that with an orifice changeable pressure type flow rate control apparatus as claimed in Claim 7, a valve body 23 of a control valve 2 which forms a pressure type flow rate control apparatus A is hermetically connected with an inlet side block 40 having a fluid flow passage 40 a, a center block 41 equipped with a valve seat 2 b and an outlet side block 42 equipped with an outlet side fluid passage 42 a.

The invention as claimed in Claim 8 is so constituted that with an orifice changeable pressure type flow rate control apparatus as claimed in Claim 7, a pressure detector insertion hole 41 e is provided to insert a pressure detector 6 of a pressure type flow rate control apparatus A on the center block 41.

EFFECTS OF THE INVENTION

A gasket type orifice 38 with regard to Claim 1 of the present invention is so constituted that an orifice plate 38 c is closely fitted with hermeticity between both orifice bases 38 a, 38 b. This makes it possible that the orifice is caught between both orifice bases 38 a, 38 b without causing deformation and the like even when it is made of a very thin metal plate or a metal film.

As a result, it becomes possible that an orifice plate 38 c having an orifice hole with very high accuracy is used, and an orifice 38 itself as a gasket can be clamped and fixed closely to a pipe passage and the like by utilizing the outside ends of both orifice bases as seal faces.

A gasket type orifice 38 as claimed I Claim 2 is so constituted that the entire periphery of an orifice plate 38 c is laser-welded to the outside face of the brim portion 38 d ₁. Therefore, just as the case of Claim 1, a gasket type orifice 38 having an orifice hole with very high accuracy can be manufactured without occurrence of thermal distortion on the orifice plate 38 c.

With a pressure type flow rate control apparatus as clamed in Claim 3 of the present invention, a gasket type orifice 38 as claimed in Claim 1 or Claim 2 is used, thus enabling to achieve to make the orifice 38 itself to be highly accurate, and to secure its hermeticity and prevent distortion nearly perfectly when an orifice 38 is fixed.

With an orifice changeable pressure type flow rate control apparatus as claimed in Claim 6 of the present invention, an orifice can be changed with extreme ease, and its hermeticity is secured and its distortion is prevented nearly perfectly at the time of the orifice being fixed. This makes it possible that a highly accurate flow rate control is performed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view in cross section of the major part of an orifice changeable pressure type flow rate control apparatus.

FIG. 2 is a cross sectional schematic diagram of a gasket type orifice in accordance with the first embodiment used in the present invention.

FIG. 3 is an explanatory drawing of a manufacturing method for a gasket type orifice in FIG. 2.

FIG. 4 is a cross sectional schematic diagram of a gasket type orifice in accordance with the second embodiment used in the present invention.

FIG. 5 is an explanatory drawing of the replacement of a gasket type orifice.

FIG. 6 is an explanatory drawing of the correction of flow rate accuracy after the gasket type orifice is replaced.

FIG. 7 is a block explanatory drawing of a conventional pressure type flow rate control apparatus.

FIG. 8 is a cross sectional schematic diagram to illustrate an example of a conventional orifice changeable pressure type flow rate control apparatus.

LIST OF REFERENCE CHARACTERS AND NUMERALS

-   -   A Orifice changeable pressure type flow rate control apparatus     -   1 Control part     -   2 Control valve     -   2 a Valve body     -   2 b Valve seat     -   6 Pressure detector     -   23 Valve body     -   35 Gasket     -   36 Gasket type filter     -   37 Gasket     -   38 Gasket type orifice     -   38 a Orifice base (1)     -   38 a ₁ Convex fitting portion     -   38 a ₂ Outside peripheral face     -   38 a ₃ Upper end face     -   38 b Orifice base (2)     -   38 b ₁ Concave fitting portion     -   38 b ₂ Inside peripheral face     -   38 b ₃ Lower end face     -   38 c Orifice plate     -   38 d Orifice base     -   38 d ₁ Brim portion     -   39 Inlet side fitting block     -   39 a Fluid passage     -   40 Inlet side block     -   40 a Fluid passage     -   40 b Leak check hole     -   40 c Gasket insertion hole     -   41 Center block     -   41 a Inlet side fluid passage     -   41 b Outlet side fluid passage     -   41 c Valve body insertion hole     -   41 d Gasket insertion hole     -   41 e Pressure detector insertion hole     -   42 Outlet side block     -   42 a Fluid passage     -   42 b Leak check hole     -   42 c Gasket type orifice insertion hole     -   43 Outlet side fitting block     -   43 a Fluid passage     -   43 b Gasket type orifice insertion hole     -   44 Fixture for a pressure detector     -   45 Fixing bolt for a pressure detector

BEST MODE TO IMPLEMENT THE INVENTION

An embodiment in accordance with the present invention is described hereunder with reference to the drawings.

FIG. 1 is a front view in a cross section of the major part of an orifice changeable pressure type flow rate control apparatus A in accordance with Claim 6 of the present invention. With FIG. 1, 1 a control part, 2 a control valve, 2 a a valve body of the control valve, 2 b a valve seat, 23 a valve body, 35 a gasket, 36 q gasket type filter, 6 a pressure detector, 37 a gasket, and 38 a gasket type orifice.

The afore-mentioned valve body 23 is formed by assembling three members: an inlet side block 40, a center block 41 and an outlet side block 42. An inlet side fitting block 39 and an inlet side block 40 are connected by a fixing bolt (not illustrated) through the mediation of a gasket 35.

The afore-mentioned inlet side block 40 and center block 41 are connected by a fixing bolt (not illustrated) through the mediation of a gasket type filter 36.

The afore-mentioned center block 41 and outlet side block 42 are connected by a fixing bolt (not illustrated) through the mediation of a gasket 37. Furthermore, the afore-mentioned outlet side block 42 and outlet side fixing block 43 are hermetically and detachably connected and fixed by a fixing bolt (not illustrated) through the mediation of a gasket type orifice 38.

The afore-mentioned blocks 39˜43 are all made of SUS316L-P (W melt) material. A flow-in side pipe fitting (not illustrated), a fluid passage 40 a, a fixing bolt screw-in hole (not illustrated) and the like are formed with an inlet side fixing block 39.

Also, a fluid passage 40 a, a fixing bolt insertion hole (not illustrated), a leak check hole 40 b, a gasket insertion hole 40 c and the like are formed with the afore-mentioned inlet side block 40.

Furthermore, an inlet side fluid passage 41 a, an outlet side fluid passage 41 b, an insertion hole 41 c for a valve body 2 a equipped with a valve seat 2 b, a gasket insertion hole 41 d, a pressure detector insertion hole 41 e, a fixing bolt screw-in hole (not illustrated) and the like are formed with a center block 41.

An outlet side fluid passage 42 a, a leak check hole 42 b, an orifice gasket insertion hole 42 c positioned on the fluid outlet side, a fixing bolt insertion hole (not illustrated) and the like are formed with the afore-mentioned outlet side block 42.

The afore-mentioned outlet side fixing block 43 is provided with an outlet side pipe fitting (not illustrated), a fluid passage 43 a, and a fixing bolt screw-in hole (not illustrated), which configuration is constituted similar to that of the afore-mentioned inlet side fixing block 39. Only the difference with the afore-mentioned inlet side fixing block 39 is that the insertion hole 43 c for a gasket type orifice 38 is formed with the fluid inlet side.

With FIG. 1, 44 designates a fixture for a pressure detector and 45 a fixing bolt for the pressure detector.

FIG. 2 is a schematic cross sectional diagram to illustrate one example of a gasket type orifice in accordance with Claim 1 of the present invention, which has been manufactured by the so-called press-fitting method.

Namely, said gasket type orifice 38, which is provided with a round-shaped orifice plate 38 c having a desired orifice diameter φ between an orifice base (1) 38 a and an orifice base (2) 38 b, is formed by means that the orifice base 38 a is press-fitted into the orifice base 38 b using a press machine with the thrust force of approximately 90N as shown in FIG. 3 so that both orifice bases are hermetically integrated and adhered.

The major members to constitute a gasket type orifice are all made of SUS316-LM (W melt).

Said gasket type orifice 38 is used with both a pressure type flow rate control apparatus in accordance with Claim 3 of the present invention and an orifice changeable pressure type flow rate control apparatus in accordance with Claim 6 of the present invention.

Namely, as shown n FIG. 2 and FIG. 3, an orifice base 38 a has an extruded fitting part 38 a ₁ on the disc-shaped lower end face, and its outer peripheral face 38 a ₂ is closely contacted hermetically with the inner wall face 38 b ₂ of the recessed fitting part 38 b ₁ formed on the upper end face of the other disc-shaped orifice base 38 b so that an orifice plate 38 c is hermetically fitted and maintained between their end faces.

There is no need to say that the ring-shaped upper end face 38 a ₃ and the ring-shaped lower end face 38 b ₃ of the assembled gasket type orifice 38 function as seal faces of the seal gasket between blocks 42, 43 respectively.

FIG. 4 illustrates a gasket type orifice 38 in accordance with Claim 2 of the present invention.

Said gasket type orifice is formed by means that an orifice plate 38 c is laser-welded W to the entire periphery of the outside face of the brim part 38 d ₁ installed on the one side of the inside of an orifice base 38 d, thus making the upper end face and the lower end face of a cylinder-shaped orifice base 38 d seal faces respectively.

An orifice base 38 d is made of SUS316L-LM (W melt), and the same quality as that of the orifice base 38 d or some other Ni—Cr alloys are used for an orifice plate 38 c which is equipped with an orifice hole having a prescribed inner diameter φ in the center.

Next, replacement (or exchange) of a gasket type orifice 38 is explained.

In case that there occur needs of replacing a gasket type orifice 38 due to changes of the flow rate of gases to be controlled or the type of gases to be used and the like, first as shown in FIG. 5, fixing bolts (not illustrated•4 pieces) connecting an inlet side block 40 and an inlet side fixing block (an inlet side base block) 39 and fixing bolts (not illustrated•4 pieces) connecting an outlet side block 42 and an outlet side fixing block (an outlet side base block) 43 are removed.

Next, a new gasket type orifice 38 is inserted inside the gasket insertion hole 42 c of the afore-mentioned outlet side block 42, and both blocks 40, 42 are, then, fixed to the fixing blocks 39, 43 respectively as before.

It is not needed at all that piping systems are removed at the time of a gasket type orifice 38 being replaced because a gas inlet side pipe and a gas outlet side pipe are both connected to the connecting joints of the inlet side fixing block 39 and the outlet side fixing block 43 respectively, and both blocks 39, 43 are not moved at all.

Upon completion of replacing the afore-mentioned gasket type orifice 38, a flow rate to be set and a flow rate to be controlled are newly adjusted. For example, as shown in FIG. 6, when a span error ΔQ exceeds specified values (e.g. ±5% F.S.), or a span error ΔQ is needed to be maintained below specified values (e.g. ±1% F.S.), data concerning a constant K essential to said gasket type orifice 38 after it being replaced are required to be registered to a control part A through the mediation of an orifice data reader, and a flow rate span error ΔQ and a flow rate linear error (not illustrated) are corrected by using data concerning a constant K essential to said gasket type orifice 38 after it being replaced so that a span error ΔQ and the like are corrected to be below the prescribed values.

FEASIBILITY OF INDUSTRIAL USE

The present invention is applicable to all the fluid equipment for which an orifice is used and fluid flow rate control apparatuses which are so constituted that a flow rate control of fluids is performed by using an orifice, and is mainly utilized in fields such as semiconductor manufacturing, chemical industry, pharmaceutical industry, food processing industry and the like. 

1. A gasket type orifice device comprising: orifice base provided with a convex portion for fitting and end faces; a second orifice base provided with a concave portion for fitting and end faces, wherein the first orifice base and the second orifice base are connected together; and an orifice plate provided with an orifice hole formed therein, wherein the orifice plate is hermetically inserted between first end faces of the first orifice base and the second orifice base, and second end faces of the first orifice base and the second orifice base are made to be sealing faces for the gasket type orifice device.
 2. A gasket type orifice comprising: a short cylinder-shaped orifice base having end faces on two sides; a brim portion projected inwardly inside and in the vicinity of one side of the short cylinder-shaped orifice base, wherein the end faces of both of the two sides of the short cylinder-shaped base are made to be sealing faces; and a thin orifice plate provided with an orifice hole formed therein is laser welded on an outside surface of the brim portion and is fixed over an entire periphery of the thin orifice plate to the brim portion.
 3. A pressure type flow rate control apparatus comprising: a control valve disposed to control flow of a fluid through a fluid passage; a pressure detector disposed to detect pressure in the fluid passage; an orifice disposed in the fluid passage; and a flow rate computation circuit and a computation control circuit operatively connected to receive pressure data from the pressure detector and to generate a flow rate control signal used to control opening and closing of the control valve, wherein the orifice is a gasket type orifice device according to claim
 1. 4. A pressure type flow rate control apparatus as claimed in claim 3, wherein the control valve includes a valve body comprising an inlet side block having an inlet side fluid flow passage formed therein; a center block equipped with a valve seat, wherein the center block is hermetically connected to the inlet side block; and an outlet side block having an outlet side fluid passage formed therein, wherein the outlet side block is hermetically connected to the center block.
 5. A pressure type flow rate control apparatus as claimed in claim 4, further comprising an installation position for receiving the gasket type orifice device, wherein the installation position is disposed between a fluid outlet side of the center block of the control valve and a fluid inlet side of an outlet side fitting block.
 6. An orifice changeable pressure type flow rate control apparatus comprising: an inlet side fitting block equipped with a coupling portion for a fluid supply pipe; an outlet side fitting block equipped with a coupling portion for a fluid takeout pipe; a control valve comprising a valve body, wherein the valve body is installed between the inlet side fitting block and the outlet side fitting block, wherein a fluid inlet side of the valve body and a fluid outlet side of the inlet side fitting block, and a fluid outlet side of the valve body and a fluid inlet side of the outlet side fitting block, respectively, are hermetically and detachably connected so as to form a flow passage so one or more gases flow through to the control valve; and a gasket type orifice device removably inserted between a gasket type orifice insertion hole provided on the fluid outlet side of the valve body and a gasket type orifice insertion hole provided on the fluid inlet side of the outlet side fitting block.
 7. An orifice changeable pressure type flow rate control apparatus as claimed in claim 6, wherein the valve body of the control valve comprises an inlet side block having an inlet side fluid passage formed therein; a center block equipped with a valve seat, wherein the center block is hermetically connected to the inlet side block; and an outlet side block having an outlet side fluid passage formed therein, wherein the outlet side block is hermetically connected to the center block.
 8. An orifice changeable pressure type flow rate control apparatus as claimed in claim 7, wherein a pressure detector insertion hole is provided on the center block and a pressure detector is inserted in the pressure detector insertion hole so that the pressure detector is disposed to detect pressure of one or more gases flowing through the control valve.
 9. A gasket type orifice device as claimed in claim 1, wherein the first orifice base and the second orifice base are connected together so that the first orifice base is press-fitted into the second orifice base.
 10. A pressure type flow rate control apparatus comprising: a control valve disposed to control flow of a fluid through a fluid passage; a pressure detector disposed to detect pressure in the fluid passage; an orifice disposed in the fluid passage; and a flow rate computation circuit and a computation control circuit operatively connected to receive pressure data from the pressure detector and to generate a flow rate control signal used to control opening and closing of the control valve, wherein the orifice is a gasket type orifice device according to claim
 2. 11. A pressure type flow rate control apparatus as claimed in claim 10, wherein the control valve includes a valve body comprising an inlet side block having an inlet side fluid flow passage formed therein; a center block equipped with a valve seat, wherein the center block is hermetically connected to the inlet side block; and an outlet side block having an outlet side fluid passage formed therein, wherein the outlet side block is hermetically connected to the center block.
 12. A pressure type flow rate control apparatus as claimed in claim 11, further comprising an installation position for receiving the gasket type orifice device, wherein the installation position is disposed between a fluid outlet side of the center block of the control valve and a fluid inlet side of an outlet side fitting block.
 13. An orifice changeable pressure type flow rate control apparatus comprising: an inlet side fitting block equipped with a coupling portion for a fluid supply pipe; an outlet side fitting block equipped with a coupling portion for a fluid takeout pipe; a control valve comprising a valve body, wherein the valve body is installed between the inlet side fitting block and the outlet side fitting block, wherein a fluid inlet side of the valve body and a fluid outlet side of the inlet side fitting block, and a fluid outlet side of the valve body and a fluid inlet side of the outlet side fitting block, respectively, are hermetically and detachably connected so as to form a flow passage so one or more gases flow through to the control valve; and a gasket type orifice device removably inserted between a gasket type orifice insertion hole provided on the fluid outlet side of the valve body and a gasket type orifice insertion hole provided on the fluid inlet side of the outlet side fitting block.
 14. An orifice changeable pressure type flow rate control apparatus as claimed in claim 13, wherein the valve body of the control valve comprises an inlet side block having an inlet side fluid passage formed therein; a center block equipped with a valve seat, wherein the center block is hermetically connected to the inlet side block; and an outlet side block having an outlet side fluid passage formed therein, wherein the outlet side block is hermetically connected to the center block.
 15. An orifice changeable pressure type flow rate control apparatus as claimed in claim 14, wherein a pressure detector insertion hole is provided on the center block and a pressure detector is inserted in the pressure detector insertion hole so that the pressure detector is disposed to detect pressure of one or more gases flowing through the control valve. 